Polymerization of olefins



Patented Dec. 1, 1942 UNITED STATE POLYMERIZATION or OLEFINS Donald R.Stevens, Swissvale, and William A.

Gruse, Wilkinsburg, Pa., assignors to Gulf Research & DevelopmentCompany, Pittsburgh, Pa., a corporation of Delaware No Drawing.

3 Claims.

This invention relates to polymerization of olefins, and it comprises amethod of treating olefinic gases for the production of low-boilingliquid polymers useful as motor fuel, which comprises bringing theolefinic gases into contact with a partially neutralized strong acid,that is to say a mixture of a strong acid such as strong sulfuric acid,benzene sulfonic acid or the like, and a salt of that acid with analkali-forming metal or radical such as sodium, potassium or ammonium;all as more fully hereinafter set forth 'and claimed.

Considerable attention has been paid in recent years to thepolymerization of olefinic gases for the production of low-boilingliquid polymers useful as motor fuel. Various thermal and catalyticprocesses have been proposedand used. Of the catalytic processes, onewhich has attained some success relies upon the use of phosphoric acidas a polymerizing catalyst. Commercial sirupy phosphoric acid (orthophosphoric acid) can be used to give a fair yield of polymers fromolefinic gases, when properly employed, and the products obtained arelargely useful as motor fuel. However, the process is subject to somedisadvantages;

react with the hydrocarbons undergoing treatment, forming sulfur dioxideand carbonization products. Strong sulfuric acid also tends to have toosevere a polymerizing efiect,producing polymers which are too highboiling to be used for gasoline motor fuel. n the other hand, dilutesulfuric acid is largely restricted in its polymerization effect toiso-butylene. Thus,, iso butylene may be polymerized to di-iso-butyleneand tri-iso ebutylene by absorption of iso-butylene in 'to per centH2804, the acid being subsequently adjusted in acidity and warmed toseparate polymerized products, as disclosed in our copending applicationSerial No. 54,336, filed December 13, 1935, said method comprising'amodification of the well knownButlerow method described in theliterature as far back as 1877..

Ourpresent invention comprises a process of polymerizing gaseous oleflnsin which the disadvantages of the processes mentioned he'reinaboveApplication October 27, 1936, Serial No. 107,905

are overcome. According to our invention, the

polymerizing agent comprises a partially neutralized strong acid such asstrong sulfuric acid, benzene sulfonic acid, toluene sulfonic acid orthe like; the partially neutralized acid having a modified'or mitigatedeffect as compared with the use of the strong acid itself, whereby thetendency toward undesirable side reactions is reduced and the extent ofpolymerization is controlled to give more volatile polymers than wouldotherwise be the case.

The partial neutralization of the strong acid may be carried out bysimply adding an alkali such as caustic soda or caustic potash, or byadding ammonia either as such or in the form of ammonium hydroxide tothe strong acid, or by simply adding to the strong acid that salt whichwould result as a product of such partial neutralization. Thus, in thecase of sulfuric acid we may add sodium sulfate or sodium acid sulfate,the'latter being preferred; in the case of benzene sulfonic acidwe mayadd sodium or potassium benzene sulfonate, andso on. In either event,the neutralization or equivalent addition of neutralization products isso carried out as to 'give a final product containing 10 per cent ormore of the normal product of neutralization, based on the amount ofacid used, up to the point of saturation.

Where a high yield of gasoline polymers is desired, the processiscarried out by subjecting olefinic gases containing butylenes orpropylene or both to contact with the partially neutralized strong acidat a suitable elevated temperature,

preferably one' suificiently high to permit volatilization and removalof polymers as they are formed, the polymers being subsequently conmaynot entirely volatilize and are separated from the catalyst in liquidform.

siderably with .the temperature employed and the results desired.Ordinarily we prefer to use to per cent sulfuric acid. However, somewhatmore dilute acid, for example down to 65 per cent sulfuric acid, may beemployed at high temperatures if desired, although a diminution in theextent of polymerization results, especially with regard to relativelydilute oleflnic gases.

The temperatures employed will depend largely upon the strength of theacid and the concentration of the oleflnic starting material, but ingeneral should be suillcient to permit vaporization and removal of thepolymers, or a desired fraction thereof. with the preferred partiallyneutralized 80 to 90 per cent sulfuric acid, temperatures may run ashigh as 200 C. even higher, while with the sulfonic acids temperaturesnot exceeding 150 C: are desirable. At the higher temperatures thepolymers formed tend to be more volatile than at the lower temperatures,other factors ,being the same.

The pressures employed in the operation may nm as high as 500'pounds persquare inch, the higher pressures being especially useful whenrelatively dilute oleflnic gases are employed as starting material, butordinarily the preferred pressure range is from 100 to 300 pounds persquare inch.

The following examples will illustrate the practice and advantages ofour invention:

3 In one example a butane cut obtained from refinery cracked gas wastreated with 90 per cent sulfuric acid. In a second example a similarand iso- -butylene being passed continuously therethrough attemperatures between 100 and 120 C. A tabulation of the results follows:

While the total yield of polymers in Example 5 is lower than in Example4, this may readily be increased by recycling or by series contact in aplurality of stages. The principal effects noted in Example 5 are thehigher volatility range of the polymers obtained and the. substantialfuric acid which had been saturated with sodium similiar cut was treatedwith 90 per cent sulfuric acid saturated with sodium acid sulfate. Atabulation of the results obtained follows:

Eminple Exiugnple Exmanple Concentration of initial sulfuric acid, percent 90 90 90 For t by weight of NaHHO4. 0 l0 sat. Temperature; .F 70 170 70 Time of contact: minutes 5 l5 5 a can we oflmsats. 71.3 77.2 78.5Color of used acid (l) v Distillation characteristics of polymers: Up to284' 1" percent 9. 5 13.0 12.0 Sitot'lli' ;percent 28.5 27.0 31.0 Above375I;peroent 62.0 60.0 67.0

1 Definite. I Slight. Dark. Light.

The above examples were batch operations carried out in a closedsystemunder only such pressure as developed therein. It will be noted that theuse of sodium acid sulfate increased the yield of polymers and reducedthe tendency toward side reactions and decomposition, as is evidencedby'the lighter color of the used acid and the lower rise in temperatureas compared with the use of the strong acid alone.

In two additional examples, iso-butylene .was contacted with benzenesulfonic acid in one instance and-with a mixture of 75 parts by weightsulfonic acid and 25 parts by weight of sodium benzene sulfonate in theother instance, the catalyst in each case being supported on pumice,

acid sulfate. A tabulation of the results follows:

Example 6 Example 7 Temperature. '1' 70 2i? Pressure: lbs. per sq. insec Yield polymers: percent of total unsats... 48. 7 6i. Distillationcharacteristics of polymers Up to 284 F.: per cent 02. 3 74. 284 to 3761!.: per cent 27. 2 23. Above 376 F.: per cent l0. 5 2.

At higher temperatures and pressures larger yields of polymers areobtained.

In Examples 1, 2, 3, 6 and '1 the butane cut employed was a refinery gasfraction containing 32 per cent iso-butylene, 32 per cent l-butene and2-butene, 5.7 per cent Cs hydrocarbons, and the balance consisting ofnormal and iso-butane. Our experience has shown that our process effectspolymerization not only of iso-butylene but also of l-butene and2-butene as well as propylene. Ethylene is less readily polymerized:

Wherever the gases to be employed contain sulfur in such form or in suchamount as to give a polymer difficult to refine in any of the ordinarymanners, it is advisable to subject the gases to a desulfurizingtreatment prior to contacting them with the catalyst. Variousdesulfurizing I methods are available, and do not require descriptionhere. Ordinarily, the polymers need only simple alkali and water washesfor refining purposes.

It may be observed-that at high temperatures and when the gases are dry,the acid mixture may tend to lose oisture and become more concentrated.In continuous operation this effect is readily overcome by addingsufllcieht moisture either to the acid or to the gases, to balance thedehydrating effect and maintain the acid at the desired concentration.

In the polymerization process described, the resultant polymers are ofexceptional value as motor fuel both by reason of their volatility andby reason of their high anti-knock value. I The absence of undesirableside reactions which would otherwise result from the use of the strongacid alone is marked; it being one or the advantages of our presentinvention that the acid-catalyst mixture is not rapidly deteriorated andis capable of being employed for extended periods; strong acid alonetends to darken considerably in use and is thereby rendered unfit forfurther use.

While our invention has been described hereinabove with reference to thepolymerization of aparticular butane cut and of iso-butylene inconcentrated form, it will be obvious that other refinery gases andother olefinic gases in general may be employed as starting materials inso far as they contain substantial quantities of poly-.

, merizable olefinic constituents, especially butylenes and propylene.

It will, moreover, be apparent to those skilled in the art that whereasour invention has been described hereinabove with reference to variousspecific operating details, by way of example, our

invention isnot in its broadest aspects limited to such operatingdetails, but may be variously practiced within the scope of the claims"hereinafter made.

. What we claim is:

1 In a process of producing liquid polymers useful as motor fuelsbypolymerizing' gaseous olefins the improvement which comprises subandan alkali salt thereof.

DONALD R. STEKENS. WILLIAM AFGRUSE.

